Fix warning on Win64

src/liveedit.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1504 matching lines @@
       - Debug::kFrameDropperFrameSize * kPointerSize  // Size of the new frame.
       + kPointerSize;  // Bigger address end is exclusive.
 
   Address* top_frame_pc_address = top_frame->pc_address();
 
   // top_frame may be damaged below this point. Do not used it.
   ASSERT(!(top_frame = NULL));
 
   if (unused_stack_top > unused_stack_bottom) {
     if (frame_has_padding) {
-      int shortage_bytes = unused_stack_top - unused_stack_bottom;
+      int shortage_bytes =
+          static_cast<int>(unused_stack_top - unused_stack_bottom);
 
       Address padding_start = pre_top_frame->fp() -
           Debug::FramePaddingLayout::kFrameBaseSize * kPointerSize;
 
       Address padding_pointer = padding_start;
       Smi* padding_object =
           Smi::FromInt(Debug::FramePaddingLayout::kPaddingValue);
       while (Memory::Object_at(padding_pointer) == padding_object) {
         padding_pointer -= kPointerSize;
       }
@@ skipping 280 matching lines @@
 
 bool LiveEditFunctionTracker::IsActive(Isolate* isolate) {
   return false;
 }
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 
 
 } }  // namespace v8::internal